Indoor localization enabled by Coded Light is known, for example as disclosed in WO 2004/057543. The working principle is simple; each lighting device installed in the ceiling has a unique identifier, which is embedded in its light output. Thus, in addition to the basic illumination function of the lighting device it is additionally employable for transmitting information. A map of all unique identifiers and their corresponding location is created, e.g. during an initial commissioning/mapping phase. During the operational phase, users have a handheld detector capable of detecting the unique identifiers and providing localization or navigation information via a user interface. Hence, by just holding the handheld detector in the hand, users can see on the user interface information related to the location or to the direction they should take.
In case of an emergency these kind of lighting devices are even more useful in guiding users, e.g. guiding them out of a building, or guiding rescue personnel through a building. This has been described in US 2012/0146804, which discloses lighting devices used for communicating emergency information and an escape guide lighting signal indicating an escape direction.
However, in some emergency situations the air is filled with smoke and the like, attenuating the light output of the lighting devices. Thereby the emergency function is deteriorated.